u-\^-^ 



112 NOKTII AMERICAN l^IPTEKA. 



and elongated, with the abdomen narrowed at the base, thick- 

 ened and curved downward toward the extremity ; with trans- 

 parent, irridescent wing, usually hyaline, but often with a spot 

 or spots toward the end, and are usually observed about decay- 

 ing vegetables, excrement, cheese, ham, etc., often in swarms. 

 The flies for the greater part, run about actively and are quick 

 in flight. The best known are the species of Piojihila, the 

 larvffi of which are so well known as "cheeseCmites." These 

 larvaB live in cheese, in ham or bacon, or in general in any 

 fatty material, and often do much damage, being especially 

 troublesome in pork-packing establishments. From the pecu- 

 liar power of leaping possessed by the maggots they are often 

 called " skippers "; the act is performed by the larvae seizing 

 with its extended mouth-hooklets the edge of the posterior 

 truncature of the body and then suddenly releasing it while 

 pulling hard. The larv;e are sonu^vvhat conical. ])oint('d 

 anteriorly, truncated behind, and al)out Ave millimeters in 

 length. They are shining and smooth ; the antennae composed 

 of two equally long joints; the mouth booklets separated, 

 shoi't and divergent; the anterior spiracles whitish, the ab- 

 dominal legs roughened, the anal segment with four fleshy 

 l)rotTd)erances. J*u])ariuni elliptic, rugose. 



TAliLK OF (iENERA. 



1. Head (l('])rcss('d ; anti'iiiup elon,ffate. ...... 2 



Head not de]M\'s,><('d ; antenna? not reacliiny licyond the oral niarti'm. ■'> 



2. Second joint of antenn;e elonj>ate, third oval. PuocirvLiZA Walker. 

 Second joint short, tiurd eloimale. . . Tvlomvia (iii-lio-'ros. 



.■;. Auxiliary vt'in di.^tinct ; ))al])i rudimentary (Nf/j.s-/(((f ). ... 4 

 j\n.\iliary vein indistinet or wantini;- (/'/('/^///////(f ). .... 5 



4. FroiU t'i'niora of the inaU's with tuliercdes on the lower sideO J^-^'^\'v \..\ (^ 



Skpsis Fallen. 

 ' Front t'ernoi-a of male without tuliercdes below. Ni:moi'OI).\ Desvoiily. 



•') F'ace (donsiate !ind truncate; ant-like in appearance. (^i:i'U vi.ia Meiiieii. 

 Face not el()nii;ate and truncate, but rounded. . . . . 'i 



